1. Field of the Invention
The present invention relates to an air conditioner constructed of a plurality of indoor units and a single outdoor unit.
2. Description of Related Art
A so-called multi air conditioner has been developed which is constructed of a plurality of indoor units each installed within a room, and a single outdoor unit. Such a multi air conditioner is provided with a refrigerating cycle including a compressor, an outdoor heat exchanger, a plurality of indoor heat exchangers, and the like. The compressor and outdoor heat exchanger are collectively installed as an outdoor unit. A plurality of indoor heat exchangers are each collectively installed as an independent indoor unit. Since the multi air conditioner has only one outdoor unit, each indoor unit cannot run in a different operation mode. For example, if a heat operation command from the controller of an indoor unit of room A and a cool operation command from the controller of an indoor unit of room B are supplied at the same time to the controller of the outdoor unit, the multi air conditioner of the type described above cannot deal with both the operation commands.
In anticipation of such a case, a conventional multi air conditioner of this type has been provided with the following control method. Namely, the priority order of operation modes for an air conditioner is determined in advance (such as in the order of heat, cool, and blow), and an operation permission command is returned back to an indoor unit which sends an operation command representative of an operation mode having the highest priority order.
If the operation mode of the multi air conditioner system is controlled by the above-described control method, indoor units other than the indoor unit having the highest operation priority enter an operation inhibition (standby) state. When the highest operation mode is cancelled (e.g., when the indoor unit assigned the highest priority stops its operation, or when it selects a lower priority operation mode), one of the other indoor units having the highest priority order at that time is selected and an operation permission signal is sent. Then, the operation mode of the multi air conditioner system changes to the operation mode designated by the indoor unit given the operation permission signal.
The time when the indoor unit having the highest priority order at the first time cancels the operation mode, corresponds to the time when an operator manipulates an operation stop key or an operation mode setting key. If the indoor unit operating under the highest priority mode cancels the mode after a long time from when a certain indoor unit sets an operation mode, the set operation mode may sometimes be improper at that time for a person in that room because of a change in room conditions. Furthermore, a person may sometimes leave the room before the indoor unit having the highest priority order cancels its operation mode. In this case, unnecessary power is consumed uneconomically. In addition, during this time period, another indoor unit cannot be operated, disabling reasonable operation of the whole system.
Furthermore, such a multi air conditioner system is designed such that the total capacity of a plurality of indoor units is larger than the capacity of an outdoor unit, because all indoor units are seldom operated at the same time. There is, however, a possibility that the total capacity of a plurality of indoor units actually exceeds the capacity of an outdoor unit. In view of this, there has been proposed an air conditioner which selectively determines indoor units to be operated in such a case (refer to Japanese Patent Laid-Open Publication No. 62-162834). According to this proposal, indoor units are selectively determined in accordance with a predetermined priority, order This conventional technique does not consider the case where system conditions change because the initially selected indoor units stop their operation, and so one or all of the other indoor units which were not permitted to be operated are allowed to start operating.